web2py SQLFORM.grid url - grid

Question

When I try to put form = SQLFORM.grid(db.mytable) in my controller the request changes to my/web/site/view?_signature=520af19b1095db04dda2f1b6cbea3a03c3551e13 which causes my if statement in controller to collapse. Can smbd please explain why this happens?
If I put user_signature=False then on view load the grid is shown (though the looks is awful, and I still need to find out how to change the view of my table), but on search,edit, etc. click, the same thing happens again. The url is changed and I get an error
Any suggestions?
thank you
EDIT
This is my edit function
#auth.requires_login()
def edit():
#Load workers
workers = db(db.worker.w_organisation == 10).select(db.worker.w_id_w, db.worker.w_organisation, db.worker.w_first_name, db.worker.w_last_name,db.worker.w_nick_name,db.worker.w_email,db.worker.w_status,db.worker.w_note).as_list()
#Define the query object. Here we are pulling all contacts having date of birth less than 18 Nov 1990
query = ((db.worker.w_organisation == 10) & (db.worker.w_status==db.status.s_id_s))
#Define the fields to show on grid. Note: (you need to specify id field in fields section in 1.99.2
fields = (db.worker.w_first_name, db.worker.w_last_name,db.worker.w_nick_name,db.worker.w_email,db.status.s_code,db.worker.w_note)
#Define headers as tuples/dictionaries
headers = { 'worker.w_first_name' : 'Ime',
'worker.w_last_name' : 'Priimek',
'worker.w_nick_name' : 'Vzdevek',
'worker.w_email' : 'E-posta',
'status.s_code': 'Status',
'worker.w_note' : 'Komentar' }
#Let's specify a default sort order on date_of_birth column in grid
default_sort_order=[db.worker.w_last_name]
#Creating the grid object
form = SQLFORM.grid(query=query, fields=fields, headers=headers,searchable=True, orderby=default_sort_order,create=True, \
deletable=True, editable=True, maxtextlength=64, paginate=25,user_signature=False
)
form = SQLFORM.grid(db.worker,user_signature=False)
workersDb = db((db.worker.w_organisation == 10) & (db.worker.w_status==db.status.s_id_s)).select(db.worker.w_id_w, \
db.worker.w_organisation, db.worker.w_first_name, \
db.worker.w_last_name,db.worker.w_nick_name,db.worker.w_email,\
db.status.s_code,db.worker.w_note).as_list()
workersList = []
for rec in workersDb:
status = rec['status']['s_code']
workers = rec['worker']
if not rec["worker"]["w_first_name"]:
polno_ime = rec["worker"]["w_last_name"]
elif not rec["worker"]["w_last_name"]:
polno_ime = rec["worker"]["w_first_name"]
else:
polno_ime = rec["worker"]["w_first_name"] + " " + rec["worker"]["w_last_name"]
rec["worker"]['w_full_name'] = polno_ime
rec["worker"]["w_status"] = status
data = rec["worker"]
#print rec
#print data
workersList.append(rec["worker"])
# If type of arg is int, we know that user wants to edit a script with an id of the argument
if(request.args[0].isdigit()):
script = db(getDbScript(request.args[0])).select(db.script.sc_lls, db.script.sc_name, db.script.id, db.script.sc_menu_data).first()
formData = str(script["sc_menu_data"])
#form = SQLFORM.grid(db.auth_user)
#print formData
# If we dont get any results that means that user is not giving proper request and we show him error
#print script
#Parsing script to be inserted into view
if not script:
return error(0)
return dict(newScript = False, script = script, formData = formData, workers = workersList, form = form)
# If the argument is new we prepare page for new script
elif request.args[0] == 'new':
scripts = db((auth.user.organization == db.script.sc_organization)).select(db.script.sc_name, db.script.id, workers = workersList, form = form)
return dict(newScript = True, scripts = scripts, workers = workersList, form = form)
# Else error
else:
return error(0)
also not to mention the sqlgrid looks awful, here is link to the picture https://plus.google.com/103827646559093653557/posts/Bci4PCG4BQQ